U.S. patent number 5,855,744 [Application Number 08/684,446] was granted by the patent office on 1999-01-05 for non-planar magnet tracking during magnetron sputtering.
This patent grant is currently assigned to Applied Komatsu Technology, Inc.. Invention is credited to Russell Black, Allan De Salvo, Richard E. Demaray, Victoria L. Hall, Harlan I. Halsey, Akihiro Hosokawa.
United States Patent |
5,855,744 |
Halsey , et al. |
January 5, 1999 |
Non-planar magnet tracking during magnetron sputtering
Abstract
The structure and method which improves the film thickness
uniformity or thickness control when using magnetron sputtering by
adjusting the distance between the magnetron or a portion of the
magnetron and the sputtering target to provide an improvement in
the film thickness uniformity. Shimmed rails, contoured rails,
contoured surfaces, cam plates, and cam plate control followers are
utilized to achieve an improvement in film thickness uniformity or
thickness control due to anomalies in magnetic field as a magnetron
assembly moves back and forth when sputtering substrates (utilized
primarily for rectangularly shaped substrates).
Inventors: |
Halsey; Harlan I. (Woodside,
CA), Demaray; Richard E. (Portola Valley, CA), Black;
Russell (San Carlos, CA), Hosokawa; Akihiro (Cupertino,
CA), De Salvo; Allan (Los Gatos, CA), Hall; Victoria
L. (Menlo Park, CA) |
Assignee: |
Applied Komatsu Technology,
Inc. (Tokyo, JP)
|
Family
ID: |
24748082 |
Appl.
No.: |
08/684,446 |
Filed: |
July 19, 1996 |
Current U.S.
Class: |
204/192.12;
204/298.12; 204/298.2; 204/298.18; 204/298.19 |
Current CPC
Class: |
H01J
37/3408 (20130101); H01J 37/3455 (20130101) |
Current International
Class: |
H01J
37/34 (20060101); H01J 37/32 (20060101); C23C
014/35 () |
Field of
Search: |
;204/298.16,298.17,298.19,298.2,298.22,192.12,298.12,298.18 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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27 07 144 |
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Aug 1977 |
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DE |
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2-290971 |
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Nov 1990 |
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JP |
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3-243762 |
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Oct 1991 |
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JP |
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5-202471 |
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Aug 1993 |
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JP |
|
Primary Examiner: Nguyen; Nam
Assistant Examiner: McDonald; Rodney G.
Attorney, Agent or Firm: Biksa; Janis Edelman; Lawrence
Claims
We claim:
1. A magnetron sputtering apparatus, comprising:
a magnet member having a magnetic field emanating therefrom
disposed in the proximity of a sputtering target,
a magnet member cycling system which during sputtering of said
sputtering target causes said magnet member to move in a set
pattern,
wherein said set pattern of motion is defined by a set of points
defining a pattern reference surface, wherein the pattern reference
surface is defined by a set of lateral coordinates and a set of
vertical coordinates of the pattern,
wherein said set of lateral coordinates establish a defined set of
locations on an offset reference surface which is approximately
parallel to a reference surface of said sputtering target and
offset from it,
wherein said set of vertical coordinates establish a defined set of
elevations for said set pattern at each respective lateral
coordinate of said set of lateral coordinates,
wherein said pattern reference surface includes a divergent portion
having a subset of said defined set of elevations establishing the
elevation of the pattern reference surface within said divergent
portion at a distance from said offset reference surface at each
respective lateral coordinate of said set of lateral coordinates,
wherein the elevation of the pattern reference surface within said
divergent portion falls outside a range of tolerance for
parallelism between said offset reference surface and said
reference surface of said sputtering target.
2. The magnetron sputtering apparatus as in claim 1, wherein motion
of said magnet member following said divergent portion of said
pattern reference surface, rather than following a non-divergent
portion of said pattern in which said distance would fall within
the range of tolerance for parallelism between offset reference
surface and said reference surface of said sputtering target,
provides an improvement in the uniformity or thickness control of
film thickness deposited on the surface of a substrate, located
opposite said sputtering target, being sputter deposited.
3. The magnetron sputtering apparatus as in claim 1,
wherein said reference surface of said sputtering target is defined
by unused pre-sputtering configuration surface of said sputtering
target facing a processing chamber.
4. The magnetron sputtering apparatus as in claim 2,
wherein said reference surface of said sputtering target is defined
by an unused pre-sputtering configuration of a front surface of
said sputtering target facing a processing chamber.
5. The magnetron sputtering apparatus as in claim 1, 2, 3, or 4,
wherein said tolerance for parallelism is 0.0075 inches per foot of
motion along said offset reference surface.
6. The magnetron sputtering apparatus as in claim 1, 2, or 3,
wherein said tolerance for parallelism is 0.010 inches per foot of
motion along said offset reference surface.
7. The magnetron sputtering apparatus as in claim 1, 2, or 3,
wherein said tolerance for parallelism is 0.015 inches per foot of
motion along said offset reference surface.
8. The magnetron sputtering apparatus as in claim 1, 2, or 3,
wherein said tolerance for parallelism is 0.020 inches per foot of
motion along said offset reference surface.
9. The magnetron sputtering apparatus as in claim 1, 2, or 3,
wherein said tolerance for parallelism is 0.025 inches per foot of
motion along said offset reference surface.
10. The magnetron sputtering apparatus as in claim 1, 2, or 3,
wherein said tolerance for parallelism is 0.030 inches per foot of
motion along said offset reference surface.
11. The magnetron sputtering apparatus as in claim 1, 2, or 3,
wherein said tolerance for parallelism is 0.035 inches per foot of
motion along said offset reference surface.
12. The magnetron sputtering apparatus as in claim 1, 2, or 3,
wherein said tolerance for parallelism is 0.040 inches per foot of
motion along said offset reference surface.
13. The magnetron sputtering apparatus as in claim 1, 2, or 3,
wherein said tolerance for parallelism is 0.050 inches per foot of
motion along said offset reference surface.
14. The magnetron sputtering apparatus as in claim 1, wherein said
set pattern of said cycling system results from a motion along a
set of tracks supporting and guiding the magnet member,
wherein the configuration of said set of tracks establishes said
set of lateral coordinates and said set of vertical coordinates of
said set pattern, including said divergent portion.
15. The magnetron sputtering apparatus as in claim 14, wherein said
motion along said set of tracks is a back and forth motion.
16. The magnetron sputtering apparatus as in claim 1, further
comprising:
a set of tracks supporting and guiding the magnet member
a cam surface fixed to a first of either said magnet member or a
fixed support adjacent said tracks and a cam follower fixed to a
second of either said magnet member or said fixed support,
wherein a divergent portion of said motion, corresponding to said
divergent portion of said pattern reference surface, results from a
motion along said set of tracks,
wherein said set pattern of said cycling system results at least
partially from a motion along said set of tracks where during said
set motion said cam follower comes into contact with said cam
surface and urges said magnet member in a vertical direction to
follow a motion corresponding to the divergent portion of said
pattern reference surface.
17. The magnetron sputtering apparatus as in claim 1,
wherein said magnet member includes a series of magnet member
subsections,
wherein said magnetron apparatus further comprises:
a set of tracks, wherein each one of said set of tracks supports
and guides a corresponding subset of said series of magnet member
subsections,
a series of cam surfaces, each one of said series of cam surfaces
being fixed to a first of either a subsection of said series of
magnet member subsections or a fixed support adjacent said tracks
and a cam follower fixed to a second of either a subsection of said
series of magnet member subsections or said fixed support,
wherein a divergent portion of said motion, corresponds to said
divergent portion of said pattern reference surface,
wherein said set pattern of said cycling system results at least
partially from a motion along said set of tracks where during said
set motion said cam follower comes into contact with said cam
surface and causes at least one of said series of magnet member
sections to move in a vertical direction to follow a motion
corresponding to the divergent portion of said pattern reference
surface.
18. The magnetron sputtering apparatus as in claim 17,
wherein said series of cam surfaces form a continuous cam plate
surface.
19. The magnetron sputtering apparatus as in claim 1,
wherein said magnet member includes a series of magnet member
subsections,
wherein said magnetron apparatus further comprises:
a set of tracks, wherein each one of said set of tracks supports
and guides a corresponding subset of said series of magnet member
subsections as a lateral drive moves each one of said series of
magnet member subsections in a lateral direction,
a series of vertical drives, each one of said series of vertical
drives being fixed to provide relative motion between each
respective subsection of said series of magnet member subsections
and said lateral drive,
wherein a divergent portion of said motion, corresponds to said
divergent portion of said pattern reference surface,
wherein said recurring pattern of said cycling system results at
least partially from a vertical motion provided by said vertical
drive as a result of programming a control of said vertical drive
to provide a preset pattern of relative motion corresponding to the
divergent portion of said pattern reference surface.
20. A magnetron sputtering apparatus comprising:
a sputtering target assembly having a first side opposite a second
side wherein a target surface on said first side is exposed to a
sputtering chamber;
a traveling magnet member disposed to travel along a track on a
second side of said target assembly, said magnet member including
components which produce a magnetic field extending beyond the
surface of said magnet member toward said target surface,
wherein a portion of said magnet member travels in a plane
approximately parallel to an unused pre-sputtering configuration of
said surface of said first side of said target, except in a
divergent portion, where the distance of a portion of the magnetic
member and said unused configuration of said surface of said first
side of said target assembly exceed a range of tolerance for
parallelism between said plane and said unused pre-sputtering
configuration of said surface of said first side of said
target.
21. The magnetron sputtering apparatus as in claim 20,
wherein travel of said magnet member following said divergent
portion, rather than following said plane, provides an improvement
in the uniformity of film thickness deposited on the surface of a
substrate, located opposite said sputtering target, being sputter
deposited.
22. The magnetron sputtering apparatus as in claim 20 or 21,
wherein said tolerance for parallelism is 0.0075 inches per foot of
motion along said track.
23. The magnetron sputtering apparatus as in claim 20 or 21,
wherein said tolerance for parallelism is 0.010 inches per foot of
motion along said track.
24. The magnetron sputtering apparatus as in claim 20 or 21,
wherein said tolerance for parallelism is 0.015 inches per foot of
motion along said track.
25. The magnetron sputtering apparatus as in claim 20 or 21,
wherein said tolerance for parallelism is 0.020 inches per foot of
motion along said track.
26. The magnetron sputtering apparatus as in claim 20 or 21,
wherein said tolerance for parallelism is 0.025 inches per foot of
motion along said track.
27. The magnetron sputtering apparatus as in claim 20 or 21,
wherein said tolerance for parallelism is 0.030 inches per foot of
motion along said track.
28. The magnetron sputtering apparatus as in claim 20 or 21,
wherein said tolerance for parallelism is 0.035 inches per foot of
motion along said track.
29. The magnetron sputtering apparatus as in claim 20 or 21,
wherein said tolerance for parallelism is 0.040 inches per foot of
motion along said track.
30. The magnetron sputtering apparatus as in claim 20 or 21,
wherein said tolerance for parallelism is 0.050 inches per foot of
motion along said track.
31. The magnetron sputtering apparatus as in claim 20,
wherein said magnet member includes a series of magnet member
subsections,
wherein movement along said track results from a programming of a
motor to raise and lower each subsection of said set of subsections
according a programmed pattern depending on the lateral position of
said magnet member as it moves laterally.
32. The magnetron sputtering apparatus as in claim 20,
wherein the magnet member includes at least two sections, wherein a
set of tracks comprising said track in a center track supporting an
end of each section of said at least two sections, said magnet
member being hinged at said center track.
33. A magnetron scanning apparatus comprising:
a magnet member running as a truck on a set of separated linear
bearing rails which are approximately parallel, where during
sputtering to improve the uniformity of film thickness sputter
deposited on a substrate opposite a target disposed between said
target assembly and said magnet member a first end of a first rail
of said set of bearing rails is raised to be further from the
target than a second end of said first rail of said set of bearing
rails.
34. A magnetron scanning apparatus as in claim 33,
where during sputtering to further improve the uniformity of film
thickness sputter deposited, a second end of a second rail of said
set of bearing rails is raised to be further from the target than a
first end of said second rail of said set of bearing rails, wherein
said second end of said second rail of said set of bearing rails
corresponds to said second end of said first rail of said set of
bearing rails.
35. A magnetron sputtering apparatus as in claim 34,
wherein a set of vertical positions of said first and said second
ends of said rails is set by a vertical travel mechanism which can
raise and lower said first and said second ends of said first and
second rails to set the tracking of the magnet member.
36. A magnetron sputtering apparatus as in claim 35,
wherein said vertical travel mechanism operates during sputtering
and tracking of said magnet member.
37. A method for selectively controlling the film thickness
deposited on a substrate during sputtering comprising the steps
of:
moving a magnet member laterally in an approximately linear pattern
in the proximity of a sputtering target and
varying the strength of the magnetic field enhancing sputtering at
the target surface as the magnet member moves laterally to deposit
a particular film thickness pattern on the substrate during
processing during sputtering.
38. The method for selectively controlling the film thickness
deposited on a substrate during sputtering as in claim 37,
wherein the step of varying the strength of the magnetic field
includes moving portions of said magnet member vertically.
39. The method for selectively controlling the film thickness
deposited on a substrate as in claim 38,
wherein the step of moving portions of the magnet member vertically
provides that the vertical distance is a distance greater than a
tolerance for parallelism between a reference plane and the plane
of motion at selected locations to vary the magnetic field strength
causing a divergence from the plane to control the film thickness
uniformity.
40. The method for selectively controlling the film thickness
deposited on a substrate during sputtering as in claim 37,
wherein the step of varying the strength of the magnetic field
includes changing the strength of electromagnets in said magnetic
member according to a pattern depending on the lateral location of
the magnet member.
41. A method for selectively controlling the film thickness
deposited on a substrate during sputtering comprising the steps
of:
moving a magnet member laterally along an approximately linear
track and
moving portions of the magnet member in a vertical direction
simultaneously with the lateral motion of the magnet member to
change the magnetic field intensity utilized for sputtering at one
or more locations along the track to improve the control of the
film thickness deposited during sputtering.
42. A method for selectively controlling the film thickness
deposited on a substrate during sputtering comprising the steps
of:
locating a magnetic field opposite a sputtering target;
moving the magnetic field laterally across the target;
varying the strength of the magnetic field at locations where a
localized change in the deposited film thickness is desired
wherein the step of varying the strength of the magnetic field
includes changing the strength of electro-magnets in said magnetic
member according to a pattern depending on the lateral location of
the magnet member.
Description
FIELD OF THE INVENTION
This invention relates to the field of magnetrons and particular
configurations for their use with sputtering chambers to control
film thickness for sputter deposited film. In particular this
invention relates to controlling the deposited film thickness on
substrates by varying the distance between a portion of the
permanent magnets comprising the magnet array in the magnetron and
the sputtering target as the magnetron moves laterally across the
back of the sputtering target during sputtering.
BACKGROUND OF THE INVENTION
Sputtering describes a number of physical techniques commonly used
in, for example, the semiconductor industry for the deposition of
thin films of various metals such as aluminum, aluminum alloys,
refractory metal suicides, gold, copper, titanium,
titanium-tungsten, tungsten, molybdenum, tantalum and less commonly
silicon dioxide and silicon on an item (a substrate), for example a
substrate or glass plate being processed. In general, the
techniques involve producing a gas plasma of ionized inert gas
"particles" (atoms or molecules) by using an electrical field in an
evacuated chamber. The ionized particles are then directed toward a
"target" and collide with it. As a result of the collisions, free
atoms or neutral or ionized groups of atoms of the target material
are released from the surface of the target, essentially liberating
target material are released from the surface of the target,
essentially liberating atomic-level particles from the target
material. Many of the free particles which escape the target
surface condense and form (deposit) a thin film on the surface of
the object (e.g. wafer, substrate) being processed, which is
located a relatively short distance from the target.
One common sputtering technique is magnetron sputtering. When
processing substrates using magnetron sputtering, sputtering action
is concentrated in the region of the magnetic field on the target
surface so that sputtering occurs at a higher rate and at a lower
process pressure than possible without the use of magnets. The
target itself is electrically biased with respect to the substrate
and chamber, and functions as a cathode. Objectives in engineering
the cathode and its associated magnetic field source include
uniform erosion of the target and uniform deposition of pure target
material on the substrate being processed.
If, during sputtering, magnets generating a magnetic field are
stationary at a location, then continuous sputtering consumes a
disproportionate fraction of the sputtering target thickness at
that location quickly and generates hot spots at the locations of
sputtering. Therefore magnets are continuously moved across the
back side of the target in a path designed to cause uniform
utilization of the target's surface and sputter deposit a
correspondingly uniform film thickness on the substrate being
processed. Sputtering a target creates a deposition pattern on the
substrate which generally matches the utilization (erosion) pattern
on the target surface.
To avoid contamination of the processing chamber and substrate
processed therein, sputtering is stopped before the non-uniform
sputtering wear pattern has consumed the full thickness of the
target material at any point. If any point on the plate behind the
target were to be reached, sputtering of the target backing plate
material (often copper) would occur, contaminating the vacuum
chamber and the substrate being processed with the target backing
material. Because of the non-uniform pattern of target utilization,
sputtering is usually stopped when a large percentage of the target
remains.
As the target erodes, the distance between the target surface
(which is eroding away) and the substrate being sputtered is slowly
increasing. The change in the distance between the target surface
and the substrate being sputtered creates a change in the qualities
of the sputtered material deposited and its uniformity. When
material is deposited on large areas such as glass plates,
variations in the thickness of deposited sputtered material are
measurable and, may be unacceptable.
In generating the gas plasma and creating ion streams impacting on
the cathode, considerable energy is supplied. This energy must be
dissipated to avoid melting or nearly melting the structures and
components involved. A common technique used for cooling sputtering
targets is to pass water or other cooling liquid through a fixed
internal passage of the sputtering target. Another cooling
technique which is commonly used is to expose a back side of a
target to a cooling bath. Cooling liquid circulating through the
bath container assists in controlling the temperature of the back
of the target assembly. A magnet assembly (magnetron) located on
the back side of the target with a backside cooling bath moves
within the liquid of the cooling bath.
FIGS. 1, 2, and 3 show a prior art sputtering chamber 50 in which a
rectangular substrate 64 (shown in dashed lines in FIG. 1) is
supported on a pedestal 52. A target assembly 58, consisting of a
target backing plate 56 and a target 54 having a front face facing
the pedestal 52, covers the upper flange of the processing chamber
sealing it. On the side of the target assembly opposite from the
pedestal 52 a magnetron chamber 60 encloses a magnetron assembly
62. The magnetron chamber 60 can be made vacuum tight to reduce the
differential pressure across the target assembly 58 (with cooling
fluid being routed through the target assembly), or it can be
filled with cooling liquid to provide a cooling bath in contact
with the back side of the target assembly 58. To enhance sputtering
of a rectangular shaped substrate 64 (generally matching the shape
of the outside of the chamber 50) the magnetron assembly 62 is a
linear bar with rounded ends. The magnetron assembly 62 moves in a
horizontal, back and forth (reciprocal) pattern within the
magnetron chamber 62 as shown in by the arrows 68. The magnetron
assembly passes through the magnetron chamber 62 and to the dashed
outline of the magnetron assembly 62a. The outline of the area
covered by magnetron movement is shown by the dashed line 66.
The magnetron assembly 62 as shown in FIG. 3 runs parallel to the
target assembly 58 along one of a range of elevations between the
low and high extremes (e.g., 96, 98), which are greatly exaggerated
in this figure. The particular elevation (e.g., 96, 98) is
dependent on the desired distance 92 from the front face of the
target 54, which in turn determines the degree of sputtering
enhancement desired for a particular process chamber pressure and
sputtering process being used.
A conceptualized illustration of the magnetic field present around
the strong Neodymium Boron Iron magnets used in the magnetron
assembly is shown in the cross section of FIG. 4. The positive
poles 72, 74, 76, 78 of the magnets shown, e.g., 70, are on the top
(away from the sputtering target) in the outside loop 84 (FIG. 1)
of permanent magnets and on the bottom (close to the sputtering
target) in the inside loop 82 (FIG. 1), although the polarities may
be reversed. A magnet backing plate 80 bridges the magnetic field
on the top side of the magnetron thus preventing the magnetic field
from extending up from the top side of magnetron assembly. In
contrast, the magnetic field on the bottom side between adjacent
magnets is conceptualized by the loops 86 showing a diminishing
magnetic field strength farther down from the magnetron assembly
62. The loops of the magnetic field lines 86, portray a
comparatively strong magnetic field in the loop 88 adjacent to the
magnets, and drop off in the magnetic field strength rapidly as a
function of the distance to a comparatively weakened magnetic field
strength at the loop 90 farthest from the magnets. (The loops show
an approximation of the diminution of the magnet field strength
with distance). Any vertical movement of the magnetron assembly 62
that increases the distance between the front face of the target
and the magnetron assembly 62 from the distance 92 (FIG. 3) to the
distance 94 (FIG. 5), reduces the magnetic field strength at the
surface of the target facing the pedestal 52 by a factor of
approximately 5, relative to the range of field strength loops
shown in FIG. 4.
FIG. 6 shows a target erosion profile for a target of 6061 Al in
2000 kilowatt hour power range. The contours shown by the plot show
a generally uniform utilization of the target with a slight
increase in erosion near the ends of the profile (a dwell
location). The pattern observable from at the dwell locations
corresponds to the shape of the magnet field emanating from
magnetron assembly. The target erosion profile as shown here is
related to the rate of deposition and film thickness uniformity or
thickness control on a substrate being sputtered located opposite
such a target (areas showing greater erosion on the target result
in areas having greater deposition on the substrate). In this
particular instance, there are two areas of relatively high
erosion, one at the upper right corner 242 and the other at lower
left hand corner 244 of FIG. 6, which produce corresponding
deposition thickness anomalies on the substrate being
sputtered.
The current specifications for target film thickness uniformity
(even for large plates, such as the 50 by 60 centimeter plate shown
in FIG. 6) is 5% or better. The anomalies of high erosion at the
corners of the target as shown by the regions 242, 244 cause great
concern in meeting the specification as they distort the film
thickness uniformity so that a film thickness uniformity of only
approximately 7% can be achieved. To improve uniformity the
excessive erosion in the two regions 242, 244 must be reduced or
eliminated so that the specification for film thickness uniformity
can be met.
The observation of the high erosion in the corners has initiated a
great deal of scrutiny without an identification of its true
source. The positioning of an array of permanent magnets in the
magnetron assembly assures a uniform magnetic field throughout the
magnetron assembly. The general uniformity of the magnet field
emanating from the magnetron is confirmed by the generally uniform
erosion profile across the center of face of the target.
Speculation about the source of the reason for the anomaly in the
corners included research to determine whether a source of
electrical or magnetic field anomalies could be identified. None
has been identified.
FIG. 7 is a plot representing the film thickness on the surface of
a substrate. It confirms the uniformity of the film thickness on
the surface of a rectangular substrate. This plot shows an
approximately mirror image correlation with the target erosion
profile of FIG. 6.
In the field of thin film deposition, a size of substrates is
becoming larger and larger since there is increasing need for
larger size LCD screen. For example, current substrate size for
production is up to 400 mm.times.500 mm, however, the size will be
expanded up to 600 mm.times.700 mm or larger in the future.
One of the most difficult tasks in thin film deposition is how to
achieve uniform deposition over a substrate. This shortcoming
becomes the dominant factor preventing the economical production of
larger and larger LCD screens.
The shortcomings in film thickness uniformity or thickness control
of the existing sputtering target systems as described above
continue to inhibit the wide use of sputtering as an efficient and
cost-effective means for applying surface coatings on large
substrates.
SUMMARY OF THE INVENTION
A structure and method according to the invention reduces the film
thickness anomalies as discussed above.
Where target erosion anomalies occur, a change in the strength of
the magnetic field exposed to the target at those locations has
been found to improve the uniformity or control the variation in
thickness of the deposited film. One way to change the film
thickness at any such location is to provide a localized change in
the magnetic field strength while maintaining the uniformity of
magnetic field strength over the rest of the target area.
A magnet member (the magnetron assembly) is located in proximity to
the sputtering target, and is provided with a magnetic member
cycling system (drive system), which causes the magnet member to
move in a set or recurring pattern. The recurring pattern is
defined by a set of points defining a pattern reference surface.
The pattern reference surface is defined by a set of lateral
coordinates and a set of vertical coordinates of the pattern. The
lateral coordinates establish a grid defining the lateral locations
at which the vertical coordinates define a set of elevations of the
pattern reference surface, either on the reference surface or on an
offset reference surface (which is parallel to but offset from the
reference surface).
The pattern reference surface includes a divergent portion (a
preset pattern of relative motion) having a subset of elevations
which fall outside a range of tolerance for parallelism between the
pattern surface and a reference surface of the sputtering target.
Movement of the magnetron in the divergent portion reduces or
increases the magnetron field strength at the surface of the
target.
The reference surface of the sputtering target can be its front
face. It could be a middle axis of the sputtering target, or it
could be a back face. It should be obvious to persons of ordinary
skill in the art that the intensity of the magnetic field should be
approximately equal over the surface of the sputtering target
facing the sputtering chamber. Therefore, the definition of the
reference surface of a sputtering target can be any surface real or
imagined that can be defined generally by geometric or mathematical
means as being parallel to the surface of a sputtering target,
whether that surface be straight or curved. It is assumed that such
a straight or curved surface is a continuous one (without sudden
steps) and is generally used as a reference for parallelism before
sputtering occurs (an un-used pre-sputtering configuration),
because after sputtering has begun the target erosion will deform
the shape of the sputtering target and start to generate
differences in the uniformity of film thickness due to small, but
detectable, differences in the target erosion rate across its
surface.
It may be desirable to have uniform film thickness over some
portions of the substrate and have varying thicknesses in other
regions. The structure and method according to the invention allows
control of the film thickness deposited, by varying the strength of
the magnetic field. An approximately uniform film thickness can be
achieved, but so can a prescribed pattern of film thickness which
is not necessarily uniform, for example one which is thicker at the
edges to provide an easier connection to external wiring.
In one configuration, a change in the magnetic field strength can
be accomplished when using a two bearing rail system merely by
tilting opposite corners of opposing rails in opposite directions
(the magnetron acting as a bearing truck between the rails). For
example, by providing a high end and a low end on one bearing rail
while the opposite bearing rail has its low end opposite the high
end of the first bearing rail. Such a tilted configuration will
cause a flight path or surface pattern (profile) for the magnetron
assembly that includes regions of the surface pattern that fall
outside a standard tolerance for parallelism between the magnetron
path pattern reference surface and the reference surface of the
target. In one configuration the magnetron is tilted in one
direction at one end of the back and forth travel, and is tilted in
the opposite direction at the opposite end of the back and forth
travel. A change in rail elevation as small as 0.020"-0.030"
(500-750 .mu.m) in central regions of the travel has a noticeable
effect because of the strength of the magnetic field decreases
greatly over a small distance. The effect of a change in the
elevation of a linear rail of 0.030" end to end of a 2-foot travel
path provides an improvement in the variation in film thickness
uniformity from approximately 8% to approximately 3-4% (providing a
improvement which meets the 5% specification).
In another configuration, according to the invention, it is
possible that when utilizing two bearing rails that they be curved
or otherwise patterned to move the magnet member (magnetron
assembly or one end of the assembly) close to and away from the
target surface in a particularly described pattern to increase and
decrease the magnetic field strength to promote an improvement in
the control or uniformity of the deposited film thickness.
Utilizing a magnet member moving in the transverse (lateral)
direction, it is possible to provide several tracks (more than two)
to help guide the magnet member. The magnet member (magnetron) can
be divided into two or more sub-sections to assist in maintaining a
uniform target profile. For example, it is possible to provide
three generally parallel bearing rails (a set of tracks) which
support two magnet member sub-sections between them. The outside
bearing rails can be relatively flat, while the inside bearing rail
could dip down or rise up to change the magnetic field intensity.
Similarly, the magnet member could be constructed of a series of
magnet member sub-sections (connected in a housing or separate from
one another) with each magnet sub-section following the contour of
its own rail or path as it moves from one end to the other end of
the processing chamber.
In another configuration, a cam plate surface which includes a
series of slots and surface followers which are connected to the
subsections of the magnet member. Movement of the magnet member
from one end to the other causes the elevation of each separate
sub-section of the magnet member to follow the pattern of the cam
surface. Varying the elevation of various magnet subsections by the
use of a mechanical cam surface--follower system can also be
reproduced by utilizing vertical activation devices such as motors
and vertical drives which cause each magnet member subsection to
move vertically according to a pre-programmed contour depending on
its lateral location. Such movement could potentially change the
sputtering intensity at the ostensible location of sputtering
anomalies, which create an uneven erosion profile, to eliminate
such anomalies and improve the film thickness uniformity.
It is known that the distance between the face of the sputtering
target and the substrate being sputter deposited is one factor in
determining the film thickness deposited on the substrate. However
when sputtering large substrates, because the center of the target
is farther away from the source of sputtering power, and there
tends to be a drop in the sputtering intensity at the center of a
large target. Therefore, to compensate for this drop, the magnet
field at this location (region) could be gradually increased by
moving the magnetron closer to the sputtering target at the center
to improve the film thickness uniformity.
Another configuration for improving film thickness uniformity is to
tilt (roll or pitch) only the end of the magnetron near the end of
its travel. The bearing rails supporting the magnetron are kept
straight and level and the end of the magnetron is tilted by
utilizing a localized ramp (cam) and roller (cam follower). Either
the ramp or the roller is located on the end of the magnetron and
the ramp or follower is located on a stationary support fixed to
the processing chamber. The lateral motion of the magnetron at a
particular location causes the cam to engage the cam follower
causing a tilting force to be generated. The tilting force pushes
the end of the magnetron in a vertical direction to cause the
magnet member reference surface to describe the divergent portion.
The tilt can be a roll motion or a pitch motion as the terms roll
and pitch are understood when referring to an aircraft's
attitude--the magnet member (magnetron) relating to a fixed wing on
an aircraft.
Electromagnets can be used in the magnetron and the magnetic field
of the electromagnets can be varied to cause changes in the
strength of the magnetic field to affect and control the film
thickness desired.
A method according to the invention includes the steps of moving a
magnet member laterally in the proximity of a sputtering target and
moving portions of said magnet vertically, a distance greater than
a tolerance for parallelism between a reference plane and the plane
of motion at selected locations to vary the magnetic field strength
causing a divergence from the plane to improve the film thickness
control. Another method according to the invention includes the
steps of moving a magnet member laterally along a track and moving
portions of the magnet member in a vertical direction
simultaneously with the lateral motion of the magnet member to
change the magnetic field intensity utilized for sputtering at one
or more locations along the track to improve film thickness
uniformity for sputtering.
These structures and methods provide a degree of improvement in the
control of film thickness not known or utilized in the prior
art.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic top view of a prior art magnetron
enclosure;
FIG. 2 is a cross sectional end view of the sputtering chamber
separated from the prior art magnetron chamber of FIG. 1 by the
target assembly;
FIG. 3 is a side cross sectional view of the apparatus of FIG. 2
showing the conceptualized magnetic field of the magnetron
extending far beyond the sputtering target;
FIG. 4 is a cross sectional view of the magnetron including
permanent magnets and a conceptualization of the magnetic field
emanating downwardly therefrom;
FIG. 5 is a second side cross sectional view of the apparatus of
FIG. 2 showing the magnetron raised up to a higher elevation with
the conceptualized magnetic field from the magnetron just barely
extending beyond the sputtering target;
FIG. 6 is a prior art target erosion profile showing the pattern of
erosion (utilization) of the sputtering target during
sputtering;
FIG. 7 shows the film thickness profile on a substrate as
determined from a sheet resistance analysis using a five point
probe (which is inversely proportional to film thickness) for a
sputtering target utilizing the prior art magnetron chamber;
FIG. 8 is a plot of the film thickness contours of a sputtering
target assembly from a sheet resistance analysis using a five point
probe (which is inversely proportional to film thickness) when
using a structure and method according to the invention;
FIG. 9 is a schematic perspective view of a magnetron chamber
utilizing a center bearing rail to support the magnetron;
FIG. 10 is a schematic representation showing an exaggerated
dimension of the center magnetron support beam of FIG. 9 and its
rotation as it travels along the center beam support;
FIG. 11 is a cross sectional view of a magnetron support beam taken
at 11--11 of FIG. 14;
FIG. 12 is a cross sectional view of a magnetron support beam taken
at 12--12 of FIG. 14;
FIG. 13 is a cross sectional view of the magnetron support beam
taken at 13--13 of FIG. 14;
FIG. 14 is a top view of a magnetron chamber according to the
invention with a center magnetron support beam;
FIG. 15 is a perspective view of a bearing channel beam with
bearing tracks (rails) supported on the central beam as shown for
example in FIG. 9;
FIG. 16 is a modified bearing support rail showing the channel
being split and being raised one side of each end of the channel to
provide the vertical travel of portions of the magnetron;
FIG. 17 shows a top plan view of the end of the magnetron as shown
in FIG. 18 as it about to engage the ramp (cam) to be lifted;
FIG. 17A shows a top plan view of the end of the magnetron as shown
in FIG. 18A as it about to engage the ramp (cam) to be lifted;
FIG. 18 is a partial cross sectional view of a magnetron chamber
taken at 18--18 of FIGS. 20 and 24, showing the ramp which raises
the end of the magnetron at opposite ends of the chamber;
FIG. 18A is a partial cross sectional view of a magnetron chamber
taken at 18A--18A of FIGS. 20A, showing the ramp which tips the
edge of the magnetron at opposite ends of the chamber;
FIG. 19 shows a cross sectional side view showing the position of
the ramp in relation to the magnetron;
FIG. 20 shows the top plan view of the magnetron chamber having a
magnetron whose ends are subject to being raised by ramps at
opposite corners;
FIG. 20A shows the top plan view of the magnetron chamber having a
magnetron whose ends are subject to being raised by ramps at its
corners;
FIG. 21 shows a schematic cross section of a deformable horizontal
magnetron whose end is bent up in a curved shape, taken at 21--21
in FIG. 24;
FIG. 21A shows a schematic cross section of a rigid horizontal
magnetron whose end is raised up, taken at 21--21 in FIG. 24;
FIG. 22 is a schematic cross sectional view of the deformable
horizontal magnetron, taken at 22--22 in FIG. 24;
FIG. 22A is a schematic cross sectional view of the rigid
horizontal magnetron, taken at 22--22 in FIG. 24;
FIG. 23 is a cross sectional view of the deformable horizontal
magnetron whose end is bent up, taken at 23--23 in FIG. 24;
FIG. 23A is a cross sectional view of the rigid horizontal
magnetron whose end is bent up, taken at 23--23 in FIG. 24;
FIG. 24 is a schematic top view of a magnetron chamber where the
magnetron is supported near its center, including ramps at opposite
corners to influence the vertical position of the end of the
magnetron when the magnetron is moved near either end of its
travel;
FIG. 25 is a bottom plan view of a magnetron chamber utilizing a
central beam support for the magnetron track;
FIG. 26 is a cross sectional view of the magnetron chamber of FIG.
25;
FIG. 27 is a schematic perspective view of a magnetron chamber
enclosing a traveling magnetron supported by two horizontal beams
near its ends;
FIG. 28 is a schematic representation of the elevation change
(rotation) of the magnetron as it travels one end to the other
along inclined tracks as shown in FIG. 27;
FIG. 29 is a schematic cross sectional view of a magnetron
supported from two generally parallel rails (tracks) according to
the invention;
FIG. 30 is a cross sectional view showing the magnetron support
rails and magnetron attitude, taken at 30--30 in FIG. 33;
FIG. 31 is a cross sectional view showing the magnetron support
rails and magnetron attitude, taken at 31--31 in FIG. 33;
FIG. 32 is a cross sectional view showing the magnetron support
rails and magnetron attitude, taken at 32--32 in FIG. 33;
FIG. 33 is a schematic top view of a magnetron chamber where the
magnetron is supported near its ends by two horizontal support
rails;
FIG. 34 is a bottom plan view of a magnetron supported along two
generally parallel beams at the edges of the magnetron chamber;
FIG. 35 is a cross sectional end view of FIG. 34;
FIG. 36 shows a cross sectional view of a hinged magnetron in a
magnetron chamber, for example as shown in FIG. 37;
FIG. 37 shows a schematic perspective view of a hinged magnetron
with a bowed down center track according to the invention;
FIG. 38 shows a moving magnetron assembly (device) having permanent
magnet sub-sections whose vertical travel is influenced by a
contour plate which changes the vertical spacing between each
magnet sub-section and the target during sputtering as the
magnetron moves laterally;
FIG. 38A shows a moving magnetron assembly (device) having a
deformable magnetron connected through several cam follower
linkages to a contour plate, the vertical travel of portions of the
magnetron connected to the cam follower linkages is influenced by a
contour plate which changes the vertical distance between each
portion of the magnetron and the target during sputtering as the
magnetron moves laterally;
FIG. 39 provides an alternate conceptualized magnetron reference
surface pattern for a contour plate showing high points at the
right and left corners and low points at the front and back corners
of the conceptualized plate shown;
FIG. 40 shows a conceptualized magnet reference surface pattern
having a lateral central axis in a parabolic or circular concave
down type shape with all paths perpendicular to the lateral axis
being equal lengths;
FIG. 41 shows a conceptualized magnet bowl-shaped type parabola
pattern plate for use as a magnet section guide, the shape being
similar to the shape pictured in FIG. 38;
FIG. 42 shows a conceptualized reference surface pattern convex
surface to use as a magnet pattern contour plate;
FIG. 43 shows a flat magnet contour plate assembly utilizing
activators for raising and lowering the magnet sections
individually using electrical or other activators according to a
pre-programmed pattern;
FIG. 44 shows an magnetron whose magnets are electromagnets, the
strength of the magnetic field is controlled by varying the
electrical energy supplied to each electromagnet segment in the
magnetron as the magnetron moves laterally during sputtering;
and
FIG. 45 shows a cross section of an electro-magnetic magnetron
according to the invention as used in the configuration of FIG.
44.
DETAILED DESCRIPTION
An understanding of the improvement the invention provides results
from comparison of the film uniformity plots of FIGS. 7 and 8. In
the plot 250 of FIG. 7 the plots of the contour shows several heavy
black contour lines showing the film thickness variation across
areas of the substrate as the thickness is plotted from a center to
an edge of the substrate. The non-symmetrical (skewed) plot shows
that the upper left corner and the lower right corner depositions
include severe variations at those locations. The variation in film
thickness uniformity for the analysis of FIG. 7 being approximately
8%. In comparison a similar plot 260 using a structure and method
according to the invention results in the film uniformity plot as
shown in FIG. 8. The plot from the analysis is now generally
symmetrical about the center and is rectangular without being
skewed. The thickness variation from center to the edge being
approximately equal on both sides of a vertical center axis. FIG. 8
provides a smaller distance between the maximum and the minimum
than the plot of FIG. 7. The resulting variation in film thickness
uniformity being approximately 4%.
Single Beam Bearing Support
FIG. 9 shows a perspective schematized view of a device according
to the invention wherein a magnetron assembly 272 is moved within a
magnetron chamber 270 in the direction shown by the arrows 274. The
magnetron assembly 272 is supported on a central bearing support
beam 276 which can be moved vertically uniformly as shown by the
arrows 278. A set of bearing rails, (e.g., 382, 384) supports the
magnetron assembly 272 through a set of bearing truck receiving
members (e.g., 282). The lateral motion of the magnetron assembly
is produced by turning a threaded drive rod 284 which is engaged
with a threaded drive nut 286 contained in a threaded drive nut
housing 288. The threaded drive nut housing engages and can slide
vertically on a pair of connecting pins 290a, 290b, which are fixed
to and extend upwardly from the top of the magnetron assembly 272.
The sliding connection between the connecting pins 290a, 290b and
the threaded drive nut housing 288 accommodates differential
vertical motion between the threaded drive rod 284 which is fixed
to the walls of the magnetron chamber 270 and the magnetron 272
supported by the support beam 276. The sliding connection allows
vertical motion of a portion of the magnetron as it cycles from end
to end and tips as it cycles as shown in FIG. 10.
FIG. 10 shows an idealized exaggerated schematic perspective view
of the motion of the magnetron assembly as shown in FIG. 9. The
magnetron assembly 300 moves laterally (horizontally in this case,
but the lateral motion could be across a curved (e.g., spherical)
substrate surface as well) supported on a central bearing support
rail 302 showing a twist from end to end. Dashed lines 304, 306
show a change in the elevation of the ends of the magnetron
assembly (roll--as that term is understood for aircraft motion) as
the magnetron 300 moves laterally from one end of the chamber to
the other. As the magnetron assembly 272, 300 moves from one end of
the processing chamber to the other, its left and right ends rise
and fall, respectively, thus becoming farther from and closer to
the target assembly, respectively. The end (a portion) of the
magnetron assembly that is farther from the target surface reduces
the magnetic field influence enhancing sputtering, while an end of
the magnetron that is closer to the target surface increases the
magnetic field influence enhancing sputtering. This end to end
tilting arrangement provides greater influence on sputtering at
opposite corners of opposite ends of the magnetron chamber and
magnetron respectively as the member moves from laterally from end
to end.
Conventional thinking requires the magnet field strength to be held
constant over the whole area of the target as the magnetron moves.
Such thinking imposes a specification for flatness of the tracking
or parallelism between the path of the magnetron and a reference
surface (usually the front surface) of the target. The parallelism
between members is intended to provide a constant magnetic field.
Specification of the range of the usual tolerance for flatness or
parallelism which is usually approximately 5 thousandths of an inch
in 1 foot or less, is utilized to help define an aspect of the
invention according to the claims. Such tolerances also exclude
variations in alignment due to natural variation in manufacturing
and practical limits in aligning of mechanically mating pieces. The
actual difference in elevation of the ends of the magnetron
according to the invention can be quite subtle. Variations in
elevation slightly falling outside the natural range of the
tolerance of the specification for flatness or parallelism as
slight as 0.0075" per foot will have an effect on film thickness
uniformity, because the magnetic field strength varies strongly
with the distance. A localized variation in elevation will have a
localized effect. The localized variation can be defined as a
divergent portion (that portion of the reference surface of the
magnetron motion that exceeds the tolerance for flatness or
parallelism, both of which under normal circumstances are defined
as plus or minus 0.005" elevation variation per lateral foot or
less, less than 0.05%).
Therefore a configuration according to the invention can be defined
in terms of the tolerance for flatness or parallelism. The
imaginary surface formed by the lateral and vertical motion of the
magnetron is evaluated for flatness or for parallelism against a
reference surface. A configuration according to the invention
provides that the imaginary surface include a divergent portion
which has vertical components of the imaginary surface which fall
outside the range of the conventional tolerance for flatness and/or
parallelism and as a result of the motion of the magnetron in the
divergent portion the motion produces an improvement in the
uniformity of film thickness deposited on a substrate. Because the
magnetic field strength varies strongly as a function of distance
from the magnetron, progressively larger departures from flatness
or parallelism create progressively larger changes in the film
thickness achieved. A departure from flatness or parallelism of
0.030" at the end of the magnetron track, or as much as
approximately 10 mm out of plane at the end of the magnetron, for
the configuration of FIG. 9, results in changes in film thickness
uniformity at opposite corners of the substrate and target which
provide an observable improvement when compared to the plot of
FIGS. 7, (the setup in FIG. 7 having the normal maximum range of
0.010" from rail end to rail end, when the tolerances for flatness
or parallelism are met). The elevation change provides an
improvement in film thickness uniformity to meet the specification
requirements of a 5% variation, as shown in FIG. 8.
While this example provides one configuration of the invention,
this same technique can be used at other locations where the film
thickness uniformity or thickness control needs to be improved. The
motion of the magnetron is adjusted so that the imaginary surface
pattern describing its motion includes divergent portions which
exceed the normal tolerances for flatness or parallelism and create
a change in the magnetic field at the surface of the target being
sputtered, so that the film thickness uniformity or thickness
control deposited on the substrate is improved.
The vertical motion of a portion exceeding the specification for
flatness and for parallelism from end to end and side to side is
measured against an imaginary reference surface superimposed on the
imaginary reference surface pattern/profile created by the motion
of the magnetron assembly 272. An elevation view showing the
characteristics of the motion of the magnetron assembly 272
departing from flatness or parallelism is shown in FIGS. 11, 12,
and 13 for tilting of a linear magnetron assembly 272, and in FIGS.
21, 22, and 30 for the bending of the magnetron assembly 272. In
both configurations the ends of the magnetron assembly 272 near the
end of its travel is raised to exceed the normal (or otherwise
selected) tolerance (e.g., 0.005"/ft, 0.0075"/ft, 0.010"/ft,
0.015"/ft, 0.020"/ft, 0.025"/ft, 0.030"/ft, 0.0035"/ft, 0.040"/ft,
or 0.0050"/ft (producing an approximately 10 mm change in elevation
at the end of the magnetron)) to provide an improvement in the film
thickness uniformity or thickness control across the surface of the
substrate which is being sputter deposited.
FIG. 11, 12, and 13 are progressive sectional cuts showing the
attitude (tilt or bend--roll) of a magnetron assembly 272 as it
moves from one end to the other end of the magnetron chamber 270 as
shown in FIG. 9. The center support rail 276 supports a one-piece
bearing frame 380 as shown in FIGS. 9 and 15. Generally speaking,
the bearing rails 382, 384 are constructed to be fixed parallel to
one another. However, if a portion of the bearing rail as shown in
FIG. 16 is cut along a split separation 392 in the top of the
channel, between the holes pictured therein, and shims typically
multiples of 0.010" up to 0.060" depending upon the process, e.g.,
0.050", for example 394, 396, are positioned and fixed in place
between the center bearing support beam 276 and the one-piece
bearing frame 380 on opposite sides at opposite ends. The shims
cause a slight vertical bend in the bearing rails 382 and 384. The
slight vertical offset 371 (FIG. 13) at the center bearing support
is amplified as the magnetron projects further outward towards its
end, where the vertical offset is a maximum (approximately 10 mm).
The configuration of the bearing rails 382, 384 causes the
magnetron assembly 272 to follow the path of the rails. Movement of
the magnetron creates a series of points in an imaginary surface
pattern (flight path) tracing the position of each point of the
magnetron assembly 272 as it moves laterally. Some of the points in
the imaginary surface pattern are vertically offset from an
imaginary horizontal plane (in which the magnetron assembly would
move if its bearing rails were not vertically offset from the
neutral axis 368 (see FIG. 12) of the lateral motion and
intersecting with the pattern of the horizontal reference plane) a
distance greater than a tolerance for flatness or parallelism with
a reference surface. The vertical adjustment to the bearing rail
position can also be done by using vertical slots through which
bolts are tightened in the side of the one-piece bearing frame
instead of or in addition to the shims 394, 396.
As shown in FIG. 13, the offset in the vertical direction of the
left side split bearing rail frame 360 in a vertical direction by a
distance 370 causes the magnetron assembly to assume a roll
attitude as shown by the dashed line 372. The offset of the bearing
rail from a central axis 364 is set by a distance 366. Similarly in
FIG. 11 a right side split bearing rail 362 is shown such that the
offset of the bearing rail on the right side from a central axis
368 by a distance 371 (approximately 10 mm) provides a magnetron
roll attitude as shown by the dashed line 374. Thus, a small change
in elevation near a central support will provide a much larger
change in elevation at the extreme end of the magnetron assembly
272 extending out far beyond the central support rail 276.
FIGS. 17-20, 17A, 18A, 20A, and 21-24 show another configuration of
a magnetron supported on a central support beam 276 according to
the invention. In this configuration instead of tilting the bearing
rails, the bearing rails are maintained in their original flat
horizontal attitude which without interference would provide a
planar flat travel path for the magnetron parallel to a reference
surface of the target assembly. In this configuration the magnetron
assembly 272 is supported not just from the central bearing support
beam 276, but as the magnetron assembly approaches the ends of the
chamber a cam follower (roller) 442 engages a ramp (cam) 422 so
that the end of the magnetron assembly is bent or tilted upwards
away from the sputtering target assembly. Ramps 422, 428 are
positioned at opposite corners of the chamber, corresponding to the
locations on the sputtering target where the excessive erosion
anomaly is observed (FIG. 6). In one configuration a rigid
generally non-deformable magnetron housing can be used with a
spring loaded joint to hold the magnetron to the bearing trucks of
the center bearing rails. The springs are loaded to hold the
magnetron straight and level with the bearing rails, and to allow
hinging with a pivot axis at the center bearing rail when the end
of a magnetron comes in contact with a cam to raise it. In another
configuration the magnetron housing is made of an easily deformable
plastic, rubber or other similar material, with a rigid connection
at the center rail to the center bearing truck(s), such that when
the magnetron end comes in contact with a cam (i.e., 422) it bends
in a curve and to raise the end of the magnetron away from the
target assembly. Compare the roll attitudes shown in FIGS. 21
versus 21A and 23 versus 23A.
FIGS. 17, 17A, 18, 18A, 19, 20, and 20A are a series of related
cross sectional schematic views showing the motion of the end of
the magnetron assembly 272 where a cam (ramp) and cam follower
(roller) positioned a certain locations causes the whole magnetron
or a portion of the magnetron to move toward or away from the
target assembly. The magnetron assembly uses a cam follower
(roller) 442 and cam surface (ramp) 422 to produces a vertical roll
motion with a dimension 432 as shown in FIG. 17. The end 440 of the
magnetron assembly 272 includes a lift roller assembly frame 444
having a lift roller 442. The lift roller 442 and frame 444 travel
with the magnetron assembly 272 at its ends (only one end 440, is
shown), and when the lift roller 442 encounters the lift ramp 422
fixed to the chamber through a support fixture (e.g., support block
446), it rolls up the ramp 422 and as it is rolling up the ramp the
end of the magnetron assembly is bent up a distance 432. In this
configuration the translational force moving the magnetron assembly
272 from end to end also causes an end (e.g., 440) of the magnetron
to be bent upwards when the ramps 422, 428 are encountered. The
dashed lines, 424, 420, 430 in FIGS. 21, 22 and 23 represent the
idealized bent, straight, and bent attitude (configurations),
respectively, of the magnetron assembly 272 as it moves from end to
end. In the idealized case, one side of the magnetron assembly 272
remains straight and parallel with the reference surface of the
target assembly while the other side is bent up in a curve
approximately as shown (the linear horizontal dashed lines are a
reference against which the change in elevation at the end of the
magnetron assembly can be evaluated), in practice there will be
some impact on the free end of the assembly as there is some play
between the linear bearings in the truck and the bearing rails and
some vertical motion at the free end will occur.
In the top view of FIG. 24, probable locations for an upper left
corner ramp 422 and a lower right corner ramp 428 are shown (the
locations providing elastic bending of the magnetron assembly
without excessive material stress--for example when an easily
deformable material such as rubber is used). When the magnetron
assembly 270 moves from its centrally located horizontal attitude
(configuration) 420 taken at 22--22 in FIG. 24 to a first end of
the chamber as shown by the attitude taken at 21--21, the resulting
bending of the magnetron assembly is shown by the dashed line 424
and provides an offset dimension 426 from the center line (e.g.,
420) at the end of the magnetron assembly. Similarly when the
magnetron assembly 272 moves to the other end of the chamber as
shown by the view taken at 23--23, the bent attitude of the
magnetron assembly is shown by the dashed 430 provides a
dimensional offset 432 from the center line (e.g., 420). In a
symmetrical system the vertical offset dimensions 432, 426 due to
the bend of the magnetron assembly at the two ends should be nearly
identical, however it is possible to have a different vertical
offset dimension at each end should empirical data show that such
varying offsets are necessary. The control of sputtering to achieve
non-uniform film thickness in a prescribed pattern can also be
performed.
The illustrations of FIGS. 17A, 18A, and 20A show the use of four
ramps (or cams) 415, 416, 417, 418, with a spring loaded center
magnetron connection to the center bearing rails trucks (not shown
here). The ends of he magnetron the top view of which is shown in
FIG. 17A includes two sets of rollers 434, 436 which are located
above a side of the magnetron 272a. When the magnetron nears the
end of its lateral travel two of its rollers on one side (only one
of which is shown, e.g., 434) contacts two ramps (i.e., 415, 418)
and the magnetron undergoes an upward pitch to raise the edge of
the magnetron nearest to the edge of the chamber by a distance
432a. This edge rise due a change in the pitch (again using an
aircraft attitude reference) of the magnetron cause a reduction in
the magnetic field at the edge of the target assembly and avoids
excessive deposition due to edge effects which might otherwise be
present. Thus the magnetron can undergo changes in its roll and
pitch attitudes. A change in its yaw attitude would be possible if
the bearing tracks were not generally linear or if the bearing
trucks included a suspension allowing for some differential motion
between adjacent bearing truck on a magnetron.
The conceptualized configurations of magnetron assemblies described
above are carried out in practice by mechanisms as shown in FIGS.
25 and 26.
FIGS. 25 and 26 show the bottom and cross sectional views of a
magnetron assembly 118 supported by a central bearing support frame
136 consisting of a linear bearing support section 142 and a
lateral extension section 144. The linear bearing support section
142 has fixed to each of its sides bearing rails 138, 140 (a set of
tracks). The magnetron assembly 118 is supported from the bearing
rails 138, 140 through a set of linear rail trucks 120, 121. The
linear rail trucks are fixed to the magnetron assembly 118 and
slide back and forth on the linear rails 138, 140. The motion of
the magnetron assembly in a back and forth (lateral) direction is
accomplished by rotation of a threaded drive rod (ball screw) 112,
which is received by a ball screw receiving nut 122 that includes a
set of nut housing pin receiving holes 126, 128. A set of drive
pins extend vertically from the magnetron assembly 118 into the
holes 126, 128 to slide vertically to avoid binding in the
mechanism due to misalignment between the linear rails 138, 140 and
the rotatable threaded drive rod 112. The threaded drive rod is
turned by a ball screw drive motor 114 supported outside the
chamber top while the second end of the ball screw is supported by
a ball screw end bearing 116. In this configuration, the movement
of the central bearing support frame 136 in a vertical direction is
accomplished by rotating a set of vertically oriented lead screws
148, 150, 152, to which toothed drive belt pulleys have been
attached. A drive pulley and motor 156, are linked to the toothed
drive belt pulleys by a toothed drive belt 154. When the belt drive
pulley and motor 156 are turned, the pulleys 148, 150, 152 turn
simultaneously to turn equally pitched lead screws engaged with
stationary nuts to move the central bearing support frame 136 up
and down while maintaining parallelism between the linear bearing
support section 142 and the target.
In a conventional configuration, the horizontal attitude of the
magnetron assembly 118 is controlled through the sliding attachment
to the very precisely aligned bearing rails 138, 140.
In this way, the movement of the magnetron assembly is uniform and
parallel with the usually flat front face of an unsputtered target
prior to its being eroded or utilized. This configuration is used
for sputtering of relatively small rectangular substrates up to
approximately 400 mm.times.500 mm in size.
In the instance when the magnetron is to be tilted using a
configuration according to the invention, the bearing rails 138,
140 are tilted (for example as shown by the configuration of FIG.
22), while the central bearing support frame 136 continues to be
moved up and down while being held in a parallel attitude with the
target assembly.
A method according to the invention includes vertically moving the
magnetron assembly as shown in FIGS. 25 and 26, as the magnetron
assembly moves laterally across the target assembly. However, given
the variations in the depth target erosion profile as shown in FIG.
6, a parallel lifting of the magnetron assembly would not provide
an improvement in the variation in film thickness uniformity or
thickness control over the current vertically fixed arrangement. An
alternate arrangement would be to drive each vertical support by
separate motor/actuators, to control the vertical motion of the
support beams and the magnetron assembly through electronic
controls tied to the lateral position of the magnetron
assembly.
Two Parallel Beam Bearing Supports
For large rectangular substrates approximately 600 mm.times.700 mm
in size, a second mechanism shown conceptualized in FIGS. 27, and
28 and in detail in FIGS. 34 and 35 is utilized.
FIG. 27 shows the context of this second mechanism of the
invention. A magnetron chamber 310 contains a magnetron assembly
312. The magnetron assembly 312 is supported by two bearing support
beams 316, 317, which allow the magnetron assembly 312 fixed to a
set of bearing trucks (e.g., 324) to move along a set of bearing
rails (e.g., 322) in a lateral direction as shown by the arrows
314. The vertical movement of the bearing support beams 316, 318 is
shown by the arrows 320. The lateral motion of the magnetron
assembly 312 along the bearing rail 322 is produced by rotation of
the threaded drive rod 326 which engages a threaded drive nut 328
contained within a threaded drive nut housing 330. The threaded
drive nut housing 330 is fixed to a bowed section of a flexible
spring-like connection 332, which is fixed to the magnetron
assembly 312 such that misalignment or relative motion between the
bearing support beams 316, 318 and threaded drive nut 326 provides
a flexible connection in a vertical direction while providing
rigidity in a transverse direction. The idealized tracking of the
magnetron assembly 312 in the configuration of FIG. 27 is shown in
FIG. 28. In FIG. 28 a magnetron assembly 342 is supported on two
bearing support rails 344, 346 supported by end frames 348, 350.
The end frames 348, 350 in this configuration being level and
parallel with each other. The positioning of the left side rail 344
showing a vertical progression of the left end of the magnetron 342
from a lower edge of the frame 348 to an upper edge of the frame
350 at the opposite end. The positioning of the right side bearing
support 346 shows vertical progression from an upper edge of the
end frame 348 to a lower edge of the end frame 350 at the opposite
end.
A magnetron assembly supported by end rails is shown in FIGS. 29
through 33. FIG. 29 shows the cross section of a processing chamber
with the magnetron assembly 312 supported by two perimeter support
rails 400, 402. This configuration is consistent with the
conceptualized visualization of FIGS. 27 and 28. At one extreme end
as can be seen in FIG. 30 (taken at the location of 30--30 in FIG.
33), the offset of the end of the rail 402 in a vertical direction
an amount shown by the distance 408a results in a magnetron
assembly attitude (tilt) as shown approximated by the dashed line
412. At a central location as can be seen in FIG. 31 (taken at the
location of 31--31 in FIG. 33) a horizontal attitude 404 configures
the magnetron to be parallel with the target surface or target
reference surface (usually a plane). At the second end of the
processing chamber as shown in FIG. 32, the cross section taken at
32--32 of FIG. 33, the position of the bearing rail 400 above the
reference plane (e.g., parallel to 404 in FIG. 31), of the target
assembly causes the attitude (tilt) of the magnetron assembly 312
to be approximately as shown by the dashed line 414. The vertical
offset distance is represented by 408b. In this instance the
horizontal offset from a lateral center line 406 of the processing
chamber is a distance 410, therefore the vertical offset dimensions
at the beam 408a 408b must be larger to achieve a similar change in
attitude (tilt) when compared to the configuration of the magnetron
assembly as is shown in FIGS. 11 through 16 where a smaller
vertical offset at the bearing rail located closer to the opposite
support rail results in a similar attitudinal change (tilt) per
unit length from one end to the other end of the magnetron assembly
312.
The detailed views of FIGS. 34 and 35 show a magnetron assembly 178
as implemented in a magnetron chamber to be with a sputtering
chamber. A magnetron assembly 178 (two alternate positions of which
are shown in FIG. 34) is supported on a set of two bearing rails
206, 208, which are supported on a set of pseudo parallel edge
bearing supports 198, 200. A set of linear rail trucks 180, 182,
engage the bearing rails 206, 208, and move back and forth as
driven by a threaded drive rod (ball screw) 172 (shown only by a
dashed line in FIG. 34). In this mechanism, the back and forth
motion of the magnetron assembly 178 is accomplished by the
rotation of the drive rod 172 mounted between a ball screw drive
motor 174 and a ball screw end bearing 176. The ball screw 172
engages a ball screw receiving nut 184 captured in a ball screw nut
receiving housing 186. The ball screw receiving housing 186 is
fixed to a flexible leaf spring-like connector 188 which is
connected to the magnetron assembly 178 near its ends. The bearing
rails 206, 208 as in the above mentioned mechanism are precisely
aligned to be parallel with one another and with the face of a
target being sputtered so that uniform deposition on a substrate
can take place.
The magnetron assembly of FIGS. 34 and 35 is supported on bearing
supports 198, 200 aligned to one another to act as a frame together
with a set of end support frame members 202, 204. To provide
vertical adjustment, four bearing mounted threaded support rods
engaged with thread receiving nuts on the frame are fixed to
toothed pulleys 210, 212, 214 and 216. A toothed drive belt 222
runs around the toothed pulleys 210, 212, 214, and 216 and around
to idler pulleys 218, 220 to engage and be driven by a belt drive
pulley and motor 224. When the belt drive pulley and motor 224
turn, each of the lead screws in the four corners are turned by the
toothed pulleys fixed to the lead screws to cause parallel
adjustment of the bearing support frame in a vertical direction. An
alternate arrangement would be to drive each vertical support by
separate motor/actuators, to control the vertical motion of the
support beams and the magnetron assembly through electronic
controls tied to the lateral position of the magnetron
assembly.
Two-Piece Hinged Magnetron
Another configuration for a magnetron assembly 460 and its vertical
manipulation is shown in FIGS. 36 and 37. These Figures show a
cross section of a hinged magnetron assembly 460 utilizing a center
support rail 462 which can be continuously bent as shown in FIG. 37
or can be a series of linear segments. In these configurations a
center intersection of the two hinged sections of the magnetron
assembly 460 are supported from the center bearing rail 462 to
provide variations in the distance from the sputtering target to
the center of the magnetron assembly 460 as the magnetron assembly
cycles from end to end. The variation in horizontal distances due
to the different horizontal dimensions when comparing a hinged
magnetron and a straight magnetron is accommodated by curving the
perimeter bearing beams inward or by providing a fixed connection
between the a bearing truck attached to the center support rail 462
while the bearing truck connections to the side support rails 464,
466, are free to move (slide) toward and away from the center
bearing rail 462, details of such connections can be developed and
executed by persons of ordinary skill in the art.
Segmented Magnetron Following Reference Contour
Another embodiment according to the invention is pictured in FIG.
38. In this embodiment one or more cam surfaces and cam followers
are utilized to change the distance between portions of a magnetron
assembly having magnetron sub-sections which can move independently
while maintaining a semblance of a continuous loop of adjacent
permanent magnets in the magnet array in the magnetron. The magnet
sub-sections (a series of magnet member subsections) can be
pivotable and can be hinged together like a chain, to provide a
continuous magnetic field, or can be encased in a flexible housing.
As shown in FIG. 38, several cam surfaces (a series of cam
surfaces) can be combined to form a continuous cam surface plate
476 reflecting the profile/pattern to be followed by each
sub-section of the magnetron and the magnetron assembly as a whole.
The cam surface plate 476 includes several adjacent cam surface
slots (e.g., 478) through which a cam follower rod (e.g., 474)
connects a cam follower (e.g., 482) with a sub-section (e.g., 472)
of the magnetron assembly. A magnetron contour tracking frame 486
maintains the vertical alignment between the cam followers (e.g.,
482) and magnetron sub-sections (e.g., 472) so that they track
together (as driven by a lateral drive) to provide an improvement
in the control of film thickness and/or its uniformity. Each track
of the profile-surface pattern varies the distance between each
particular sub-section (e.g., 472) of the magnetron assembly and
the target below.
Another configuration according to the invention is shown in FIG.
38A. In FIG. 38A a magnetron 488 is constructed of a flexible
material such that each vertical control member (of a series of
vertical drives) controls the vertical elevation of a portion of
the magnetron 488. The tracking frame 486 is cut away for clarity.
In this configuration, the influence of the magnetron 488 on the
target can be precisely controlled, by increasing the number of
vertical control members (push/pull rods) and/or by providing such
vertical control members on each side of the magnetron so that a
desired pitch attitude can be achieved.
FIGS. 39-42 show conceptualized idealized approximations of three
of a variety of surface patterns/profiles that might be utilized
for the cam surface 476.
In FIG. 39 a surface pattern/profile has a shape similar to the
surface pattern/profile tracked by the magnetron assembly of the
configuration as shown in FIGS. 9-15 (opposite corners being high,
while adjacent opposite corners are low). In this profile a back
corner 494 and a front corner 498 are low, while a right side
corner 492 and a left side corner 496 are raised. Therefore, the
elevation change between the rails which ostensibly connect the
bottom corner 498 with the right corner 492 is from low to high,
while the rail which connects from back corner 494 to left corner
496 is from high to low.
FIG. 40 shows a surface following a two dimensional circular or
parabolic shaped curve. A high point of the curve and the arc
shaped surface is along the center lateral axis 503. In practice, a
bearing rail elevation would follow a edge of the pictured surface,
for example from the right corner 504 to the bottom corner 510 and
from the top corner 506 to the left hand corner 508.
The surface profile/pattern contour of FIG. 41 shows an upwardly
parabolic or rounded type shape where all of the corners, right
corner 516, back corner 518, left corner 520, and front corner 522
are approximately at equal high elevations, while a center 515 of
the corners is at a low point. A magnetron assembly following this
surface pattern will have magnet sub-sections in the magnet array
of the a magnetron assembly which cause the center portion of the
magnet array to approach the back of the target to increase the
sputtering at that location. Alternately, the configuration may be
used so that the magnetic field effect uniformly sputters a
circularly or parabolically shaped target to sputter deposit a
similarly shaped circularly or parabolically shaped substrate
(e.g., a parabolic mirror) without having to form a specially
shaped magnetron. In using this configuration the deposition film
thickness can be kept relatively constant utilizing a magnetron
sub-section surface pattern/profile as shown by FIG. 41.
FIG. 42 shows a concave down circular or parabolic surface shape
with four corners 528, 530, 532 and 534 being the low point of the
surface profile/pattern, while a high point of the surface
profile/pattern is at a center 527.
A person of ordinary skill in the art will understand that the
mechanical cam shape (e.g., of FIG. 38) or any generally reasonably
continuous cam surface profile/pattern can be utilized to change
the distance between the magnetron sub-sections and the target
assembly. The surface patterns/profiles shown are but several of
the many varieties of surface patterns that might be utilized.
Variations in the cam surface/profile can accommodate desired
localized changes in the sputtering rate at those particular
locations by forming the cam surface accordingly.
Vertical Actuators
Another configuration of the device according to the invention is
to utilize a planar follower plate 546 which utilizes an
approximately flat plate and a structure which correlates a lateral
position and a vertical position of each sub-section (e.g., 542) of
the magnetron as shown in FIG. 43. Each sub-section (e.g., 542) is
connected through a vertical positioning rod (e.g., 544) to a
contour plate follower activator (e.g., 552). These collectively
makeup an activator assembly (e.g., 550). The activator assembly
(e.g., 550) moves in a slot (e.g., 548) in the planar follower
plate 546 according to the motion of a magnetron contour tracking
frame 558 (shown in dashed lines) which ties all of the activator
assemblies together so that they move simultaneously in a lateral
direction as the magnetron assembly (including all of the magnetron
sub-sections) sweeps laterally across the target assembly. The
vertical position of each magnetron sub-section 542 is set
according to a control system 554 which receives elevation control
data which establishes an elevation for each magnetron sub-section
location as the magnetron cycles from end to end. The elevation
control data causes the magnet sub-sections to moves in a
programmed manner according to a programmed surface
profile/pattern. The programmed pattern causes the magnet
sub-section to move as if it were following a surface pattern of a
mechanical cam surface (i.e., as shown in FIG. 38) utilizing
electronic programming to cause the activators to move the
magnetron sub-sections according to programming of a contour
generator 556, which provides a reference contour to the control
system 554. The programming of the contour data is easily changed
to adjust the magnetron tracking according to a desired surface
pattern/profile.
Electro-Magnet Magnetron Control of Sputtering
FIGS. 44 and 45 show a magnetron configuration using
electro-magnets which can be used to control sputtering. A
magnetron 560 held in a plane generally parallel to a target's
surface is swept back and forth across the back of a target
assembly. As the magnetron 560 is moved electromagnets in the
magnetron are energized and the intensity of the magnetic field
generated by each electromagnet in the array is varied according to
a contour plot 556a which sets out the desired film deposition
profile based on empirically derived knowledge of variations in the
physical configuration. Thus as the magnetron moves back and forth
the magnetic field is electrically varied to achieve a result
similar to that achieved by moving a magnetron with permanent
magnets closer to and further away from the back of the target
assembly. The magnet array in such a configuration may include a
combination of permanent and electromagnets, and such electro
magnets may be used in conjunction with a vertical motion or with
motion in a plane. In the extreme, a static array of electromagnets
could have an area covering the substrate surface and the movement
of magnetic field would be electronically controlled by controlling
the energization and deenergization of selected electromagnets.
FIG. 45 shows a configuration of the magnetron 560 utilizing
electromagnets. The magnets are aligned in the same way as shown in
FIG. 4 except that each permanent magnet segment is replaced by a
electromagnetic core (preferably iron) possibly in the shape of a
spool 564 as shown, with each spool 564 being surrounded by a wire
coil 568. The strength of the magnetic field is individually
controlled by a circuit wires 576 connected to the contour
controller 554a. As the magnetron travels back and forth the
magnetic field strength is varied by changing the electrical power
supplied to the electromagnetic coils and sputtering is enhanced
accordingly.
A method according to the invention for selectively controlling the
film thickness deposited on a substrate during sputtering includes
the steps of moving a magnet member laterally in the proximity of a
sputtering target and varying the strength of the magnetic field
enhancing sputtering at the target surface as the magnet member
moves laterally to deposit a particular film thickness pattern on
the substrate during processing during sputtering. It may be
desirable to have a different than uniform film thickness, for
example it may be desirable to increase the film thickness at the
edge of the substrate so that wiring connections between the
conductive layers deposited on the substrate have an increased
durability and are less subject to fracture. In general it is
expected that the tolerances for film thickness uniformity over a
substantial portion of the substrate will have to be maintained,
whether localized anomalies in film thickness are desired or not.
The structure and method according to the invention provides
uniformity where uniformity in film thickness is desired and
provides non-uniformity where non-uniformity is desired
A method according to the invention utilizes moving magnet sections
or magnetron assemblies laterally while utilizing a vertical
support which changes the elevation of particular portions of the
magnetron assembly according to its lateral position to improve
film thickness uniformity.
A method according to the invention includes the steps of moving a
magnet member laterally in the proximity of a sputtering target and
moving portions of said magnet vertically, a distance greater than
a tolerance for parallelism between a reference plane and the plane
of motion at selected locations to vary the magnetic field strength
causing a divergence from the plane to improve the film thickness
uniformity. Another method according to the invention includes the
steps of moving a magnet member laterally along a track and moving
portions of the magnet member in a vertical direction
simultaneously with the lateral motion of the magnet member to
change the magnetic field intensity utilized for sputtering at one
or more locations along the track to improve film thickness
uniformity or thickness control for sputtering. The magnet member
can be moved laterally along a track and while portions of the
magnet member are moved in a vertical direction simultaneously with
the lateral motion of the magnet member to change the magnetic
field intensity utilized for sputtering at one or more locations
along the track to improve the control of the film thickness
deposited during sputtering.
In a method according to the invention the step of varying the
strength of the magnetic field includes changing the strength of
electromagnets in the magnetic member according to a pattern
depending on the lateral location of the magnet member.
While the invention has been described with regards to specific
embodiments, those skilled in the art will recognize that changes
can be made in form and detail without departing from the spirit
and scope of the invention.
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